Today on the archive
Tue Aug 22 09:28:44 BST 2006
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- Title: Long Term Operation and Performance of Cryogenic Sapphire Oscillators
- Authors: M.E. Tobar, E.N. Ivanov, C.R. Locke, P.L. Stanwix, J.G. Hartnett, A.N. Luiten, R.B. Warrington, P.T.H. Fisk, M.A. Lawn, M.J. Wouters, S. Bize, G. Santarelli, P. Wolf, A. Clairon, P. Guillemot
- Abstract: Cryogenic Sapphire Oscillators (CSO) developed at UWA have now been in operation around the world continuously for many years. Such oscillators, due to their excellent spectral purity are essential for interrogating atomic frequency standards at the limit of quantum projection noise; otherwise aliasing effects will dominate the frequency stability due to the periodic sampling between successive interrogations of the atomic transition. For this reason, UWA oscillators are now operational at NMI (Sydney), LNE-SYRTE (Paris), the French Space Agency (CNES, Toulouse) and at UWA (Perth). Other applications, which have attracted attention in recent years, include tests on fundamental principles of physics, such as tests of Lorentz invariance. This paper reports on the long-term operation and performance of such oscillators. We compare the long-term drift of some different CSOs. The drift rates turn out to be linear over many years and in the same direction. However, the magnitude seems to vary by more than one order of magnitude between the oscillators, ranging from 10^14 per day to a few parts in 10^13 per day.
- Comment: Yay UWA physics!
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- Title: Tutorial on the double balanced mixer
- Authors: Enrico Rubiola
- Abstract: Smart use of mixers is a relevant issue in radio engineering and in instrumentation design, and of paramount importance in phase noise metrology. However simple the mixer seems, every time I try to explain to a colleague what it does, something goes wrong. One difficulty is that actual mixers operate in a wide range of power (150 dB or more) and frequency (up to 3 decades). Another difficulty is that the mixer works as a multiplier in the time-domain, which is necessary to convert frequencies. A further difficulty is the interaction with external circuits, the input sources and the load. Yet far the biggest difficulty is that designing with mixers requires a deep comprehension of the whole circuit at system level and at a component level. As the electronic-component approach is well explained in a number of references, this tutorial emphasizes the system approach, aiming to provide wisdom and insight on mixes.
- Comment: Could be useful in learning RF techniques, which are in turn useful for the new experiment using high repetition rate periodically pulsed excitation sources.
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